Chirality-Selected Chemical Modulation of Amyloid Aggregation.

ABSTRACT

Due to the composed α-helical/ß-strand structures, ß-amyloid peptide (Aß) is sensitive to chiral environments. The orientation and chirality of the Aß strand strongly influence its aggregation. Aß-formed fibrils have a cascade of chirality. Therefore, for selectively targeting amyloid aggregates, chirality preference can be one key issue. Inspired by the natural stereoselectivity and the ß-sheet structure, herein, we synthesized a series of d- and l-amino acid-modified polyoxometalate (POM) derivatives, including positively charged amino acids (d-His and l-His) and negatively charged (d-Glu and l-Glu) and hydrophobic amino acids (d-Leu, l-Leu, d-Phe, and l-Phe), to modulate Aß aggregation. Intriguingly, Phe-modified POMs showed a stronger inhibition effect than other amino acid-modified POMs, as evidenced by multiple biophysical and spectral assays, including fluorescence, circular dichroism, NMR, molecular dynamic simulations, and isothermal titration calorimetry. More importantly, d-Phe-modified POM had an 8-fold stronger inhibition effect than l-Phe-modified POM, indicating high enantioselectivity. Furthermore, in vivo studies demonstrated that the chiral POM derivatives crossed the blood-brain barrier, extended the life span of AD transgenic Caenorhabditis elegans CL2006 strain, and had low cytotoxicity, even at a high dosage.